Method of installation and control of underwater equipment

ABSTRACT

A method for installing underwater equipment on a previously installed underwater guide structure. The underwater equipment is divided into at least a first unit and a second unit, and the first unit is first lowered from a surface support onto the guide structure by means of a manipulator, the second unit is then lowered into place on top of the first unit, and then the two units are connected together. The underwater steps can be accomplished either by means of a remote-controlled manipulator or by a crew working in a work bell or a submersible.

United States Patent Brun et al. Oct. 21, 1975 [54] METHOD OF INSTALLATION AND 3,368,619 2/1968 Postlewaite 166/.6 O O OF UNDERWATER EQUIPMENT 3,500,906 3/1970 Petersen l66/.6 I 3,517,737 6/1970 Petersen 166/.6 Inventors: Andre Brun, Pans, France; Albert 3,643,736 2/1972 Talley, Jr...... l66/.5 Jaffe; Philippe de Panafieu, both of 3,672,447 6/1972 Kofahl l66/.6 London, England 3,682,243 8/1972 Bauer et a1. 166/.6 3,716,100 2/1973 Nelson 166/.6 [73] Asslgnee: Subsea Equipment Associates Ltd.,

Hamllton Bermuda Primary ExaminerJames A. Leppink [22] Fil d; D 27, 1972 Attorney, Agent, or FirmSughrue, Rothwell, Mion,

Zinn & Macpeak [21] Appl. N0.: 318,977

[57] ABSTRACT [30] Foreign Application Priority Data A method for installing underwater equipment on at Dec. 27, 1971 France 71.46720 Previously installed underwater guide Structure The underwater equipment is divided into at least a first 52 US. Cl. l66/.6 unit and a Second unit, and the first unit is first 51] 213 33/035 ered from a surface support onto the guide structure 58 Field of Search 166/.5-, .6 y means of a manipulator, the Second unit is then lowered into place on top of the first unit, and then 5 References Cited the two units are connected together. The underwater Steps can be accomplished either means Of a remote-controlled manipulator or by a crew working in a work bell or a submersible.

3,308,881 3/1967 Chan et al. 166/.6 10 Claims, 8 Drawing Figures US. Patent Oct. 21, 1975 Sheet 1 of 4 3,913,669

US. Patent Oct. 21, 1975 Sheet 2 of4 3,913,669

U.S. Patent Oct. 21, 1975 Sheet 3 of 4 US. Patent Oct. 21, 1975 Sheet 4 of4 3,913,669

METHOD OF INSTALLATION AND CONTROL OF UNDERWATER EQUIPMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for the installation and control of any underwater equipment, and more particularly to a method for the installation and control of an underwater oil well access equipment for the working of wells located at great depths, especially depths greater than those within access of a diver.

2. Description of the Prior Art Various systems of installation of underwater well access equipments have been proposed, but none of them can at present be employed in an economical and safe manner once the depth at the well access exceeds 150 meters.

Furthermore, even if the conventional systems can be adapted for the installation of wellhead access equipments, an extended suspension of operation of the well access will be necessary to repair any failure of any production control member at the wellhead access in question.

SUMMARY OF THE INVENTION This invention provides a method for the installation and control of an underwater oil-well head located at great depth and having its base surrounded by any structure which has served for drilling the well, characterized in that a supporting structure round the casing head is lowered in a first phase from a surface, support and by means of a remote-controlled manipulator. In a second phase and by means of a manipulator remotecontrolled from the surface a first detachable integrated unit is lowered, which has the function of serving as a seating for a second integrated unit as well as means of intermediate connection between the latter and the casing head in order both to ensure the continuity of the production passages and the opening or closing of these passages upstream of the second unit and also to ensure the continuity, opening, and closing of a gathering passage proceeding from this second unit. The gathering passage from the first unit is connected to an underwater gathering system of pipes, each passage being controlled by means of a valve operated by any suitable external manipulator. In a third phase and by means of a manipulator remotecontrolled from the surface, the second integrated unit is lowered, the latter having the function on the one hand of a production tree ensuring control of the flow in the production and gathering passages, discharge being effected normally through the underwater gathering system of pipes, and on the other hand the function of a means of intermediate connection between the well and any surface support with a view to transmitting any information on pressure, temperature, and flow and receiving from the surface any valve opening, closing, or adjusting commands. Such information can be transmitted either by means of the manipulator or withdrawal of the latter, by remote control.

The joining of the second unit to the first is facilitated by equipping each of the members, the first unit and manipulator, with a guide and protection structure so that in the course of the lowering of the second unit the latter can possibly take on a certain tilt and a certain offset relative to the axis of connection of the first and second units without risk of damage to the portions of these units employed for the connection, as is often the case when the devices to be connected at the seabed are only furnished with conventional impact dampers.

The presentation of the second unit relative to the first is perfected by guiding a frame connected to the manipulator by means of the guide structure surrounding the first unit and by displacing the manipulator connected to the surface support, laterally and vertically relative to the frame.

In advance of the first unit a structure is lowered to surround the casing head in a watertight manner whilst being supported vertically on a surface pipestring and laterally on a clamping device between the said structure and the outer conductor string so as to serve as a supporting base. The first unit is lowered by means of a diving-bell that has been allowed to rest on this base. It is then sufficient next to empty the bell by any known means and to admit to it air at atmospheric pressure and then a work-crew in order to proceed with the placing of the first unit under the control of this crew.

Replacement of all members of the installation situated on the seabed liable to become faulty isproceeded with by disconnecting the second unit from the first by means of a remote-controlled tool-carrier and by proceeding with replacement of these members at the surface.

The advantage of this method is in being able to install the equipments necessary to the exploitation of an underwater oilfield, such as a production wellhead, at great depth automatically in complete safety, the prior lowering of the first integrated unit enabling through the possibility of operating valves controlling the production passages, the avoidance of any premature setting of the well in action during the placing of the second unit and of checking straight from the surface the satisfactory operation of all the control devices of the second unit after its connection with the first.

Another advantage of this method is that, as opposed to previous methods in which in order to treat failures of a complex underwater equipment such as a wellhead or a separator one was compelled to intervene frequently over a multiplicity of devices each fulfilling a simple function and arranged so as to be accessible to intervention manually or by a manipulator, which caused numerous interruptions in production and multiplied the risks of damage or the impossibility of intervention because of bad weather, it is sufficient to proceed to the simple withdrawal of the unit containing the various control members, to replace it immediately with an identical unit in accordance with the method shown and to repair the defective unit at the surface. Another advantage of this method is in being able to proceed at the smallest cost with preventive maintenance of the most elaborate and often the least reliable underwater equipment by standard exchange at fixed intervals of the unit containing this equipment.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 shows a perspective view of the lower guide structure of an underwater wellhead access equipment;

FIG. 2 shows a perspective view of a supporting structure lowered from a surface support;

FIG. 3 shows the assembly of the structures shown in FIGS. 1 and 2;

FIG. 4 shows a partial diagrammatic view of a device ensuring locking of the tool carrying the supporting structure of FIG. 2 with the said structure;

FIG. 5 shows a view partially in section of a first alternative of the supporting structure of FIG. 2 after connection with the first detachableunit;

FIG. 6 shows a view partially in section of a second alternative of the supporting structure of FIG. 2 after connection with the first detachable unit;

FIG. 7 shows a diagrammatic elevation of the remote-controlled load-carrying tool surrounding a wellhead equipment; and

FIG. 8 shows a diagrammatic view of a device for separation of the detachable units.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. ll, 2, 3 and 4, the underwater wellhead access equipment to be installed and controlled has been described in applicants copending patent application Ser. No. 318,972 filed on Dec. 27, 1972, and titled A Well-Head Assembly. A conventional guide structure such as that shown at 1 in FIG. 1 has previously been placed on the seabed by any known means. This structure surrounds the outer conductor string 2 and comprises essentially a rigid frame 3 serving as a support to vertical guide bars 4, and a base 5.

A unit 8 having pipes 14 for gathering oil from the well head is lowered by means of a pipe column 6 or riser, including all the means of remote control and remote transmission, to which is. connected a remote controlled manipulator 7, carrying all the means of location and propulsion. The lowering of this first unit is effected without a guideline connecting the surface to the well, by neutralizing the effects of the swell by any known antipounding system and by providing at least one means enabling suppression of torque which would be exerted on the column during the movement of the ship 9 or any other surface support.

The manipulator 7, which can be of any type and comprises particularly means of self-guidance and selfpropulsion, is attached to the end of the column 6. In the example in FIG. 2 it supports a supporting connector, partly seen at 10 in FIG. 3, the unit 8 being connected to the support plate 11 in FIG. 3, the bearing I plate 64 in FIG. 5, or the support plate 75 in FIG. 6,

resting on a flange on the connector 10. The bearing plate 64 is provided with a center hole of sufficient diameter to let the upper portion of the connector 10 pass through it and to rest by its periphery on a flange l2 seen in FIG. 5 and located on the lower portion of the connector 10. The support plates 11 or 75 may be similarly supported, and, as seen in FIG. 5, the support plate 11 may also be provided with appropriate apertures 22 for the passage of the pipes 14, which are connected to gathering pipes 68, also seen in FIG. 5 can include a structure 76 for protection of the casing head 17 and guidance of a tool-carrier frame 30, FIG. 7, which will be described later. The supporting connector 10 can be connected to the plate ll, 64, or 75 in a watertight manner. It surrounds one portion of the casing head 17 while being supported on the intermediate surface casing 18, FIG. 1. When the unit 8 is sufficiently near the guide bars 4 and the skirt 13 is right over the top of all the bars, the unit 8 is orientated by means of the remote controlled manipulator 7 so that the cutaway corners 11a of the plate 11 are nearly above the bars 4. Guide surfaces such as 15, for exam- 1 ple, FIG. 2, located below the plate 11, at the instant of the lowering of the remote-controlled manipulator 7 guide the bars 4 through the holes 16, FIG. 3, provided in the plate 11. t

In the course of this lowering, the upper portion of I the connector 10 slides round the casing head 17 and is stopped by the intermediate casing 18, FIG. 1, on

controlled manipulator 7 and/or another manipulator I such as the tool-carrier 77 (shown in FIG. 4) are raised again and lowering proceeds of a first detachable integrated unit as seen in FIGS. 5, 6 and 7 and bounded in FIG. 5 between the dotted lines 62 and 63. Tool-carrier 77 or manipulator 7 is also used to install the supporting connector 10, in contrast to tool-carrier frame .30, it

which is used to lower the integrated unit 26 and to manipulate its valves, as will be described further hereinafter. As shown in FIG. 4, means are provided on'toolcarrier 77 for locking it to supporting connector 110. These means comprise spring 20, piston 19, cylinder 78, slot 10A in the supporting connector 10, and hydraulic tube 21 containing the control oil for the locking operation. The control oil is used to push the piston 19 leftwards against the bias of the spring 20 when it is desired to unlock the tool-carrier 77 from the supporting connector 10.

As the invention refers to the method of installation and control of any underwater equipment, of which the example selected in an underwater wellhead, it will be understood that the structure illustrated in FIG. 2 can take manifold forms, such as that shown in FIG. 5.;In

the structure shown in FIG. 5, connector 10 supports from the flange 12 a bearing plate 64 provided at its periphery with annular surfaces 65 and 66 constituting with the connector 10 a completely watertight unit.j

Passages such as 67 enable the connection of the gathering pipe 68 of the unit 61 to an underwater gathering system of pipes by means of connectors of any known type.

In accordance with a first variant a bell, or submersible unit, carrying the unit 61, is lowered from the ship 9 by means of the manipulator 7. As the bell can be of any known type and does not in itself form part of the invention it has not been shown. The edges of the bell,

which is guided externally by the vertical guide bars 4,

come to rest on the annular surface 65.

A work-crew lowered by any means provided with a lock chamber for connection to the bell then proceeds, after replacement of the water trapped by the bell with air at near to atmospheric pressure, to unlock the unit 61 from its support and lower it in order to fit it onto the casing head I17 and to connect the gathering pipe 68 to the passage 67. A connector 70 locks the unit 6l onto the casing head ,17. Means 71, shown schematically in FIG. 5, permit orientation of unit 61 with respect to casing head 17. The valve 72, which controls the production, A valve 73 which controls the.pipe connected to the annular space, and valve 74 which controlls the gathering pipework can be operated manually or by any sort of manipulator device.

Instead of a work-crew, a tool-carrier frame can also be employed, such as that shown diagrammatically at 30 in FIG. 7, which serves to protect and to fix in the working position the two integrated units 61 and 26. For clarity in the drawing, the frame and the two units 26 and 61 have been shown to the exclusion of any guide or protective structure. The units 61 and 26 (the outer contours of which are designated by the broken line 40) have besides been shown so as to make the valves 72, 73, 74 and 27, 28 and 29 appear opposite to corresponding actuators 34, 35, 36 and 37, 38 and 39 carried by the tool-carrier frame 30 and remote controlled by any known system.

This frame is attached to the end of the column 6 at the level of a guide and support plate 33 surrounding the collar for connecting the remote controlled manipulator 7 to the column 6. Once it has been lowered to the vicinity of the protective structure 76, precise positioning and connection of the unit 61 to the casing head is proceeded with. The frame 30 is lowered progres-' sively, the lower part of it having any kind of impactdampers as shown diagrammatically at 56, and let slide along the structure 76 until it rests on the support plate 75. Supported by a connector like the connector 10 in FIG. 5, the lower end of the unit 61 is then centered on the axis of the casing head 17 by any means, for example, by a connector 70 in FIG. 7 moved hydraulically by remote control from the surface or by an actuator on the tool-carrier frame 30, the male portion fitting onto the female portion at the top of the casing head 17.

This adjustment is enabled by the lateral displacement of the support and guide plate 33 which in turn is guided and supported by the plates 81 and 82, and the vertical displacement of jacks 32, the rods 32a of which control the engagement of the male portion of the connector 70 in the female portion at the top of the casing head 17.

Assuming that the unit 61 has been lowered onto the casing head 17 by any one of the foregoing variants, the unit 26 is lowered onto the unit 61 by means of the frame 30 while supporting this unit by the remote con trolled manipulator 7, the later being connected to the ship 9 by the column 6. When the frame 30 meets the guide structure which is associated with it, for example, the arches 79 in FIG. 6, it is guided in such a way that its axis coincides approximately with that of the axis of the unit 61. The arches 79 may be joined together by a ring member such as ring member 80, also shown in FIG. 6. The exact squaring up and connection of the unit 26 on the unit 61 is effected by any means, for example, by a connector 26a similar to that employed for the connection of the unit 61 to the casing head 17 and by the action of the jacks 32 and the plate 33.

With this same tool-carrier frame 30, lowering and attachment of the two units 26 and 61 can be proceeded with at depth after they have been previously connected together at the surface, by performing the same approach and attachment operations with the unit 61 to the bore-hole head as those which have just been described.

The system of remote control of, and remote transmission from, the underwater equipment is put into service in order to establish control of the equipment from a central control station.

During the erection, satisfactory operation of the units 61 and 26 is checked and, if necessary, the valves 72 to 74 and 27 to 29 are operated, for example, by means of the actuators 34 to 36 and 37 to 39, which may be controlled by any suitable remote control means. As these means do not form part of the invention they have not been shown and it goes without saying that any number of valves can be so operated.

After checking, the tool carrier frame 30 is drawn up again to the surface by means of the pipe column 6.

The wellhead installation having been achieved, the well is put into production from the surface support or from the oilfield well control and operation installation at the surface, by any kind of remote control and telemetering means such as those described in applicants copending patent application identified above.

In the event of damage to a part of the wellhead or of its becoming necessary to take action at the well, or at the times planned for systematic replacement of the unit 26, the intervention operations are carried out by the same means as those employed for the installation of the wellhead.

The tool-carrier frame 30 with the manipulator 7 are lowered at the end of the column 6 and the operations of disconnection of the unit 26 are carried out after guiding and placing the frame 30 onto the plate 75 in the same fashion as before. Next, closing of the valves of the units 61 and 26 proceeds by the remotecontrolled actuators 34 to 36 and 37 to 39 on the frame 30, and the connector 26a is disconnected by the same remote control means as used for connecting up.

The disconnection of the unit 61, which generally is less frequent, is likewise carried out by means of the tool-carrier frame 30 and the bell, if the latter was employed for the erection, by disconnecting the connector form the casing head 17 either by remote control or manually inside the bell.

In FIG. 8, by way of example, there is shown a jack 41 on the frame 30 for facilitating the withdrawal of the unit 26 after disconnection, by simple engagement of a cam 43 between two rollers 44 by means of the rod 42, the displacement of the upper roller bringing about the raising of the unit 26 through the rod 46 slidably mounted in the guides 47.

In applicants copending patent application identified above it is described how action can be taken at the well from the ship 9 through the units 26 and 61 without raising the latter.

Although a method has been described which applies to installation and control of an underwater oilwell head, the invention is not limited in its sole application I to installation of a wellhead but to any equipment including a separator installation for crude oil and gas, a pumping station or any underwater installations consisting of at least a first unit which has to be connected to a second unit.

What we clain is:

1. A method of installing underwater petroleum production equipment capable of operating at great depth, said method comprising the steps of:

l. lowering a guide structure from a surface support by means of a manipulator attached to a pipe column;

2. attaching said guide structure to a wellhead of an underwater oil well by means of said manipulator;

3. lowering a first unit from said surface support onto said guide structure by means of the or a further manipulator, said first unit a. being provided with a guide structure ensuring guiding of a second unit to be recited,

b. being adapted to ensure continuity of the production passage in said wellhead to said second unit, and

c. being adapted to control the closing and opening of said production passage;

4. attaching said first unit to said guide structure;

5. lowering a second unit from said surface support onto said first unit by means of a tool-carrier frame or a work crew, said second unit being adapted to ensure the operation of a production wellhead, the approach of said second unit to said first unit being effected by a. attaching the or a further manipulator to said tool-carrier frame by a mechanical connection enabling displacement of said tool-carrier frame relative to said manipulator,

b. maneuvering said manipulator above the guide structure provided on said first unit,

c. lowering said manipulator and said tool-carrier frame onto the guide structure provided on said first unit,

(1. resting said tool-carrier frame on a support plate, and

e. ensuring alignment and joining up of said first and second units by the simple approach of said second unit to said first unit and by displacement of said manipulator relative to said tool-carrier frame; and

6. attaching said second unit to said first unit.

2. A method according to claim 1, wherein the pas sage in the first unit adapted to ensure continuitybetween the wellhead and the secondunit is provided with a valve operable by an actuator outside the first unit.

3. A method according to claim 1, wherein valves in the second unit necessary to the operation of the said petroleum production equipment are actuated by corresponding actuators carried by said tool-carrier frame connected to the surface support by said pipe column, and wherein, after connection of the second unit to the first, checking of satisfactory operation of the said equipment from the surface is carried out before controlling the operation of this equipment from the surface, and then the tool-carrier frame and the pipe column are withdrawn.

4. A method of installing on a guide structure and thereafter controlling underwater equipment capable of operating at great depth and divided into at least a first unit and a second unit, said method comprising the steps of 1. lowering said first unit from a surface support onto the guide structure by means of a manipulator;

2. lowering said second unit from said surface support onto said first unit in an orientation such that corresponding portions of the two units engage each other, the approach of said second unit to said.

first unitbeing affected by a. attaching the or a further manipulator to a toolcarrier frame controlled from said surface sup port, the attachment being by means of a mechanical connection enabling displacement of said tool carrier-frame relative to said manipula:

tor,

b. bringing said manipulator carrying said second unit above a guide structure mounted on said first unit,

c. lowering said manipulator and said frame onto r 4. actuating valves in said second unit necessary to t the operation of said underwater equipment by means of corresponding actuators carried by said 2 tool carrier frame;

5. checking the operation of said underwater equip I ment from said surface support after connections of said second unit to said first unit; and

6. withdrawing said manipulator and said tool-carrier frame.

5. A method according to claim 4 wherein connection of the second unit to the first is effected by means of a tool carrier frame attached to said manipulator and remote-controlled from the surface. I

6. A method according to claim 4, wherein connec-. tion of the second unit to the first is effected by means of said tool-carrier frame.

7. A method according to claim 4, wherein the approach of the second unitto the first is affected by attaching the said manipulator to a tool carrier frame by a mechanical connection enabling displacement of the frame relative to the manipulator, bringing the said ma nipulator carrying the second unit above a guide structure mounted on the first unit, lowering the manipulator and frame onto the said structure, and ensuring exact alignment and joining up of the connection means of the first and second units at the same time while displacing the manipulator relative to the frame.

8. A method according to claim 7, wherein connection of the second unit to the first is effected by means:

of said tool-carrier frame.

9. A method according to claim 4, wherein there are provided valves enabling opening or closing of passages in the second unit, each having an external actuator carried by a tool carrier frame which is provided with carrier frame is carried by the manipulator.

UNITED STATES PATENT AND TRADEMARK OFFICE QER'HFICATE OF CORRECTION 3, 913, 669 October 21, 1975 Andre Brun et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent PATENT NO.

DATED INVENTOR(S) I O are hereby corrected 0 Column 3, line Column 4, line line line line ; line line line " line O; awn... a

s I I Column 5, line Column 6, line as shown below:

57 after "Figure 5" insert a period;

after the period insert --The support plate 11 or 75--. '13 after "can be" insert --of---; 14 after "kird" insert a comma; after "and" insert a comma; 16 after "effected" insert a comma; l7 after "manipulator 7" insert a comma; 18 after "Figure 4)" insert a comma; 41- after "Figure 5, insert --the--; 67 delete "A" and insert --a--; 68 after "and" insert --a--.

l delete "controlls" and insert --controls--; 38 delete "form" and insert --from---.

IN THE CLAIMS:

Claim 4, line 5 after "of" insert a colon.

[SEAL] A ttes t:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner uflarw'rrs and .Trarlemurkr 

1. A method of installing underwater petroleum production equipment capable of operating at great depth, said method comprising the steps of:
 1. lowering a guide structure from a surface support by means of a manipulator attached to a pipe column;
 2. attaching said guide structure to a wellhead of an underwater oil well by means of said manipulator;
 3. lowering a first unit from said surface support onto said guide structure by means of the or a further manipulator, said first unit a. being provided with a guide structure ensuring guiding of a second unit to be recited, b. being adapted to ensure continuity of the production passage in said wellhead to said second unit, and c. being adapted to control the closing and opening of said production passage;
 4. attaching said first unit to said guide structure;
 5. lowering a second unit from said surface support onto said first unit by means of a tool-carrier frame or a work crew, said second unit being adapted to ensure the operation of a production wellhead, the approach of said second unit to said first unit being effected by a. attaching the or a further manipulator to said tool-carrier frame by a mechanical connection enabling displacement of said tool-carrier frame relative to said manipulator, b. maneuvering said manipulator above the guide structure provided on said first unit, c. lowering said manipulator and said tool-carrier frame onto the guide structure provided on said first unit, e. ensuring alignment and joining up of said first and second units by the simple approach of said second unit to said first unit and by displacement of said manipulator relative to said tool-carrier frame; and
 6. attaching said second unit to said first unit.
 2. attaching said guide structure to a wellhead of an underwater oil well by means of said manipulator;
 2. A method according to claim 1, wherein the passage in the first unit adapted to ensure continuity between the wellhead and the second unit is provided with a valve operable by an actuator outside the first unit.
 2. lowering said second unit from said surface support onto said first unit in an orientation such that corresponding portions of the two units engage each other, the approach of said second unit to said first unit being affected by a. attaching the or a further manipulator to a toolcarrier frame controlled from said surface support, the attachment being by means of a mechanical connection enabling displacement of said tool carrier-frame relative to said manipulator, b. bringing said manipulator carrying said second unit above a guide structure mounted on said first unit, c. lowering said manipulator and said frame onto the guide structure mounted on said first unit, and d. ensuring exact alignment and joining up of the connection means between said first and second units by displacement of said manipulator relative to said tool-carrier frame;
 3. lowering a first unit from said surface support onto said guide structure by means of the or a further manipulator, said first unit a. being provided with a guide structure ensuring guiding of a second unit to be recited, b. being adapted to ensure continuity of the production passage in said wellhead to said second unit, and c. being adapted to control the closing and opening of said production passage;
 3. connecting said second unit to said first unit;
 3. A method according to claim 1, wherein valves in the second unit necessary to the operation of the said petroleum production equipment are actuated by corresponding actuators carried by said tool-carrier frame connected to the surface support by said pipe column, and wherein, after connection of the second unit to the first, checking of satisfactory operation of the said equipment from the surface is carried out before controlling the operation of this equipment from the surface, and then the tool-carrier frame and the pipe column are withdrawn.
 4. attaching said first unit to said guide structure;
 4. A method of installing on a guide structure and thereafter controlling underwater equipment capable of operating at great depth and divided into at least a first unit and a second unit, said method comprising the steps of
 4. actuating valves in said second unit necessary to the operation of said underwater equipment by means of corresponding actuators carried by said tool carrier frame;
 5. checking the operation of said underwater equipment from said surface support after connections of said second unit to said first unit; and
 5. A method according to claim 4 wherein connection of the second unit to the first is effected by means of a tool carrier frame attached to said manipulator and remote-controlled from the surface.
 5. lowering a second unit from said surface support onto said first unit by means of a tool-carrier frame or a work crew, said second unit being adapted to ensure the operation of a production wellhead, the approach of said second unit to said first unit being effected by a. attaching the or a further manipulator to said tool-carrier frame by a mechanical connection enabling displacement of said tool-carrier frame relative to said manipulator, b. maneuvering said manipulator above the guide structure provided on said first unit, c. lowering said manipulator and said tool-carrier frame onto the guide structure provided on said first unit, e. ensuring alignment and joining up of said first and second units by the simple approach of said second unit to said first unit and by displacement of said manipulator relative to said tool-carrier frame; and
 6. attaching said second unit to said first unit.
 6. withdrawing said manipulator and said tool-carrier frame.
 6. A method according to claim 4, wherein connection of the second unit to the first is effected by means of said tool-carrier frame.
 7. A method according to claim 4, wherein the approach of the second unit to the first is affected by attaching the said manipulator to a tool carrier frame by a mechanical connection enabling displacement of the frame relative to the manipulator, bringing the said manipulator carrying the second unit above a guide structure mounted on the first unit, lowering the manipulator and frame onto the said structure, and ensuring exact alignment and joining up of the connection means of the first and second units at the same time while displacing the manipulator relative to the frame.
 8. A method according to claim 7, wherein connection of the second unit to the first is effected by means of said tool-carrier frame.
 9. A method according to claim 4, wherein there are provided valves enabling opening or closing of passages in the second unit, each having an external actuator carried by a tool carrier frame which is provided with as many actuators as valves, with the opening or closing of the valves being effected from the surface by remote control of the said actuators.
 10. A method according to claim 9, wherein the tool carrier frame is carried by the manipulator. 